Drexel dragonThe Math ForumDonate to the Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » Software » comp.soft-sys.math.mathematica

Topic: differential equations
Replies: 1   Last Post: Jul 30, 1996 2:57 AM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
N Kinoshita

Posts: 3
Registered: 12/7/04
differential equations
Posted: Jul 28, 1996 11:23 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Hi, I am a research student of economics. I want to solve
a system of differential equations with Mathematica.

I wrote the follwoing command based on the example given
in p.698 of 'Mathematica: A system for doing mathematics
by computer'

------------------------------------------------------------
ks=0.380884;cs=0.0282254;ws=0.846308;
k0=ks/10;
cprimess=0.00778013/0.257126;
wprimess=0.966347/0.257126;

NDSolve[
{c'[k]==
If[k==ks,cprimess,
(-0.012+0.952757k/w[k]^.7+0.11938/w[k]^.6
+2.6603c[k]/w[k]^.1-0.635171w[k])
/(0.875c[k]+0.952757k^2/w[k]^.7+1.04457k/w[k]^.6
+2.6603c[k]k/w[k]^.1-0.635171k*w[k]^.3-0.447674w[k]^.4)
],
w'[k]==
If[k==ks,wprimess,
(1.1938w[k]^.4+6.65074c[k]w[k]^.9-1.58793w[k]^1.3)
/(0.875c[k]+0.952757k^2/w[k]^.7+1.04457k/w[k]^.6
+2.6603c[k]k/w[k]^.1-0.635171k*w[k]^.3-0.447674w[k]^.4)
],
c[ks]==cs, w[ks]==ws},
{c,w},{k,ks,k0}]
-----------------------------------------------------------

Then I got the error message saying:
NDSolve::deql:
True is not a valid equation or list of valid equations.

I was able to solve a single differential equation before,
but do not know how to cope with my problem now.

I would like to get some comments.









Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2014. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.